Same distance between chapter head and text / toc

Question

With the following example, I get a different vertical distance between "Contents" and "1 bar 5" and "foo" and "Lorem". How do I get the first entry of the TOC to the same height as "Lorem ipsum", that is the base line should be the red rule in the image below:

\documentclass{book}
\begin{document}
\tableofcontents

\chapter*{foo}
Lorem ipsum

\chapter{bar}
Lorem ipsum 

\end{document}

Answer 1

The command \l@chapter in book.cls typesets the chapter entry in the table of contents. It adds 1.0 em vertically before the entry. So, to remove that space before the first entry, you could redefine that macro or add a negative vertical skip before you start the first chapter, such as

\addtocontents{toc}{\vskip -1.0em}
\tableofcontents
\chapter*{foo}

Actually, the macro contains also a glue of 1 pt. From book.cls:

\newcommand*\l@chapter[2]{%
  \ifnum \c@tocdepth >\m@ne
    \addpenalty{-\@highpenalty}%
    \vskip 1.0em \@plus\p@
    \setlength\@tempdima{1.5em}%
    \begingroup
      \parindent \z@ \rightskip \@pnumwidth
      \parfillskip -\@pnumwidth
      \leavevmode \bfseries
      \advance\leftskip\@tempdima
      \hskip -\leftskip
      #1\nobreak\hfil \nobreak\hb@xt@\@pnumwidth{\hss #2}\par
      \penalty\@highpenalty
    \endgroup
  \fi}